DOT5 is fine in systems designed for it, or have ALL of the rubber conponents changed over to parts compatible with it. However, most companies do not make parts for DOT5 compatability as it is not the OEM reccomended fluid. The only company I know of for sure that did make all of their rubber parts DOT5 compatable was EIS, and they're out of business. Also, the OEMs do not suggest DOT5 in any vehicle using ABS, as it will cavitate in the module.
Like I said, though, I did try it, based on suggestions from severaly publications concerning older vehicles with open systems. The braking action was exellent, good pedal and such. But when I noticed that spot on the floor, an tracked it to the M/C, well, I got worried. I had just read an article in Brake & Front End about DOT5, which discussed problems with it, including how it damages the rubber if not 100% compatable. This convinced me to contact Wagner. They say not to use it. Raybestos says the same.
Oh, and one more thing. Yes, DOT5 will not attack the paint, but if you get it on anything that you plan to paint later, it'll cause the same problems as silicone wax products!
I'll stick with good ol' DOT3/4.
